No, one side accepts hearing as a fact only when the visual fact is removed (blind testing). Where the other side accepts that sight doesnt emasculate what we hear (sighted testing).

Well, I tend to accept what the evidence and logic supports, and remain open to varying degrees to the possibility that something as yet unsupported may be later proven correct.

All evidence so far supports the view that knowledge of the test (the euphemistic "sight") is removed, the claimed auditory differences collapse.

Now, it is a matter if logic that we can't prove the negative. Meaning that we can't prove through tests that it is impossible that anyone could truly hear differences that all previous tests say shouldn't be audible. There always exists the possibility that there is someone, somewhere, with exceptional abilities who wasn't tested.

However, claims to hear these differences are common. The claims often state the differences are easily audible. If this is so common and so easy, why can no one step forward to demonstrate this ability? After decades of this debate and decades of testing, we don't have a single well documented unqualified example of someone doing this. What does that tell you?

It leaves me only three choices. It may be there is a grand decades long conspiracy wherein anyone possessing these auditory abilities refuses to participate in controlled testing, thus making the huge sample of tested persons through the years unrepresentative of the population of audiophiles. I suspect there is another reason many refuse to participate. Another possibility is to believe that our hearing acuity is actually somehow emasculated not by biases (as you state, which is both logical and supported by evidence) but by the removal of them. Again, that robbing someone of knowledge of the answer destroys their ability to properly listen and answer the question. This theory has been proposed many times, usually in the form of the test setup being too stressful or not like casual listening, but the test can always be arranged to accommodate the listeners preferences so that is a hollow criticism.

The other option, the one I accept, is that these supposed differences simply aren't audible and the perceptions are a result of any numbers of influencing factors and biases, or at the very least the ability to hear them is exceedingly rare. It may be that you are that rare individual. I would be thrilled if someone like you were to demonstrate that. If you did, and could duplicate the same results both sighted and blinded, then I would happily accept that not only do you have truly exceptional hearing but are also immune to influences others appear not to be. That would be cool!

Well, I tend to accept what the evidence and logic supports, and remain open to varying degrees to the possibility that something as yet unsupported may be later proven correct.

All evidence so far supports the view that knowledge of the test (the euphemistic "sight") is removed, the claimed auditory differences collapse.

Now, it is a matter if logic that we can't prove the negative. Meaning that we can't prove through tests that it is impossible that anyone could truly hear differences that all previous tests say shouldn't be audible. There always exists the possibility that there is someone, somewhere, with exceptional abilities who wasn't tested.

However, claims to hear these differences are common. The claims often state the differences are easily audible. If this is so common and so easy, why can no one step forward to demonstrate this ability? After decades of this debate and decades of testing, we don't have a single well documented unqualified example of someone doing this. What does that tell you?

It leaves me only three choices. It may be there is a grand decades long conspiracy wherein anyone possessing these auditory abilities refuses to participate in controlled testing, thus making the huge sample of tested persons through the years unrepresentative of the population of audiophiles. I suspect there is another reason many refuse to participate. Another possibility is to believe that our hearing acuity is actually somehow emasculated not by biases (as you state, which is both logical and supported by evidence) but by the removal of them. Again, that robbing someone of knowledge of the answer destroys their ability to properly listen and answer the question. This theory has been proposed many times, usually in the form of the test setup being too stressful or not like casual listening, but the test can always be arranged to accommodate the listeners preferences so that is a hollow criticism.

The other option, the one I accept, is that these supposed differences simply aren't audible and the perceptions are a result of any numbers of influencing factors and biases, or at the very least the ability to hear them is exceedingly rare. It may be that you are that rare individual. I would be thrilled if someone like you were to demonstrate that. If you did, and could duplicate the same results both sighted and blinded, then I would happily accept that not only do you have truly exceptional hearing but are also immune to influences others appear not to be. That would be cool!

Here are the factors that contribute to my point of view:

1) In these tests you speak of, we dont always know the how trained the listener is.
2) In these tests, we are talking about people in a foreign environment. IMO, when you listen to music in your home, over a period of time when nothing has been changed for a lengthy period, a sudden change of any degree is vastly more apt to be distinguished than when the listening environment is new and different.
3) In the case, where the listening environment is unfamiliar, I might agree blind A/B is the best test GIVEN there is no firm footwork for distinguishing or comparing change to some deep imprint made over time.
4) But unlike these tests you speak of, most of the testing/comparing of amps are done so in our home environment. One in which we have built up a sense of what things sound like over a period of months, years, or perhaps decades. We are not doing so at some unfamiliar and neutral site.

No, one side accepts hearing as a fact only when the visual fact is removed (blind testing). Where the other side accepts that sight doesnt emasculate what we hear (sighted testing).

No, not 'only when'. If you were to bring some other evidence into play to supplement a 'sighted comparison', you might well have an argument that you really did hear different sounds. Like, you were comparing a tube amp to a solid state one. Or, to cite a trivial reason, you didn't match levels (which of course would not be evidence that the two amps intrinsically 'sound different'). Or, measurements from the two units that would indicate different frequency response, or some other difference likely to be audible.

Sighted listening evidence as the *only* evidence, is what's not really persuasive. Such comparison are quite prone to 'confounding' influences. If you don't 'accept' that , then you might as well just say scientists don't know what they're doing and that all the evidence for the utility of blind comparison methods is worthless.

And no, familiarity or expertise doesn't guarantee you immunity from confounding effects. It is not uncommon for major orchestras to conduct their auditions 'blind'. Why do you suppose that is?

2) In these tests, we are talking about people in a foreign environment. IMO, when you listen to music in your home, over a period of time when nothing has been changed for a lengthy period, a sudden change of any degree is vastly more apt to be distinguished than when the listening environment is new and different.
3) In the case, where the listening environment is unfamiliar, I might agree blind A/B is the best test GIVEN there is no firm footwork for distinguishing or comparing change to some deep imprint made over time.

I have a question for you. The difference in being able to distinguish in a familiar listening environment versus new and different environment, did you discover this by trying level matched double blind test in both environments?

1) In these tests you speak of, we dont always know the how trained the listener is.

Quite true, which is why an audiophile claiming to already hear these differences makes a better than random candidate. Objectivists keep begging them to participate in such tests. Strangely, few agree.

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2) In these tests, we are talking about people in a foreign environment. IMO, when you listen to music in your home, over a period of time when nothing has been changed for a lengthy period, a sudden change of any degree is vastly more apt to be distinguished than when the listening environment is new and different.

4) But unlike these tests you speak of, most of the testing/comparing of amps are done so in our home environment. One in which we have built up a sense of what things sound like over a period of months, years, or perhaps decades. We are not doing so at some unfamiliar and neutral site.

Well, again, while the science and all evidence so far contradicts your assumption (ie, research has shown that we actually have quite poor long term auditory memory, and differences are most easily detected with quick switching), a controlled test can be arranged so that you can listen to each device under test for as long as you like, switch back and forth as often as desired, even leave and come back another day to do more listening. You can even be given control of the volume to adjust as you wish so long as there is some randomization of starting levels with each swap to remove a possible clue. All these things researchers have found to decrease your chances of succeeding, but controlled testing can accommodate your preferred way of comparison.

In other words, I have found such reasons to stem either from a poor understanding of what controlled testing means (it isn't synonymous with ABX or any other specific method), or as an excuse to refuse participation or poo poo results of others.

I thus find it difficult to understand how you feel you can logically contradict people who have had a dozen or more amps on hand at a time to compare, and have done blind, level-matched tests of them.

You know, I used to sell stereo equipment where I had DOZENS of amps on hand.

I believe that you have already admitted that you did not do adequate level matching and did not do double blind tests, so that is pretty much that.

You have to do everything right, half-ways efforts don't count.

FWIW I and many others have done very many tests with highly trained listeners, listening to their own systems in their own listening rooms, so we don't need to go down those rabbit holes, either.

Though I must admit my bias is towards the scientific, as Bigus said, even as scientifically biased as I may be, we cannot prove a negative. We certainly, as scientists, know amplifiers measure differently. Even right down to the component level; e.g. a resistor has a tolerance to its specs. So, if we measure that exact resistor component across many different instances of the same model amplifier, it will likely measure differently. So, sure, we know there are differences between amplifiers. At a more gross level, we know that, for example, THD figures and slew rates and other measurable things are different between models. We know all sorts of things are different between two "x watts rated" amplifiers -- but we also, to date, know that in controlled experiments where both amplifiers are operated within their linear operating range that these differences are inaudible.

That said -- even removing biases, I wonder how many of these "I hear differences" things are true. Hard to drive loads, loud listening volumes at far away distances, and other factors can push some amplifiers pretty hard into their "non linear operating range." Of course, this is a place we wouldn't want to stray into because I'd guess that what amplifiers do when they are "on the fringe" can very quite a bit due to circuit design. Oscillation would, I believe, increase THD and some designs would suffer more than others, no? So, how many of these uncontrolled "studies" have truly heard differences due to the fact that two amplifiers of similar wattage spec actually had different current capabilities (which, to the best of my knowledge really is the specification that matters most, no?). Of course, that difference was audible because one amplifier was running out of steam while the other kept on chugging. Further, its presense is probably no surprise and one which a controlled study would eliminate. But, still, one that could possibly be heard in the lisenting room of an uncontrolled experiment.

I guess what I'm getting at is, in a controlled study, one would never allow the two amplifiers to exceed their linear operating range. Therefore, any real differences between them (one running out of steam while the other was still quite easily able to reproduce the signal without compromise) would be removed. That's not to say the test is flawed because, certainly, we would easily all agree that two amplifiers sound different quite quickly when one is behaving badly due to its lacking the current capacity to meet the needs placed on it while the other lacks not. Rather, it is to say that two amplifiers being similarly spec'd "x watts" may be flawed, because the "x watt" spec is bull anyway. X watts at what THD? X watts at what THD, at which frequency having how many channels driven into a resistive load of what spec? These are real differences and the "x watt" spec, in my opinion, is insufficient to qualify them. Is "x watt @ y thd" good enough? I don't know -- is it a seven channel amplifier where if all channels are driven that increases to "x watt @ z thd?" Were both "x watt @ y thd" amplifiers measured against a resistive load with the same test tone? Does it need to be "x watt @ y thd all channels driven with tone q?" What's good enough here? Of course, in a "controlled study" we just say, "don't allow the two amplifiers out of their linear range, and they'll sound the same" -- certainly, undeniably (to date) "true" with high statisical probability.

Of course, I suppose now we can head to the "but, when listening to typical music at typical volumes with normal loads at reasonable distances, you're only using p watts anyway" debate, fill in p however you'd like, lol.

I replaced a pre/pro several years ago. The new one is known for a pretty darn good analog section.

Same room, same speakers etc. I had okay imaging prior to the change. Messed around with speaker placement and adjustments often. Wasn't bad and was acceptable. Sounded quite good in stereo but was never really like when I auditioned the speakers in a great room.
Updated pre/pro, was really quite shocked and the improved imaging when I first fired it up. Lead vocals now dead center. I didn't require a blindfold for this. It's been a really great stereo and HT processor.

The image/soundstage should be determined by the source material and sonic cues contained within, not from quirks of gear in the reproduction chain. Getting the room, speakers, and their interaction right, so that they get out of the way of the music, is the hard part. Audibly transparent electronics is the easy part.

With all due respect, you're going to lose this argument. The only real question is how long do you want it to go on?

Jim's ABE's (attitudes, beliefs & experiences) are being challenged. Most people get defensive in this kind of situation, but I seriously think that he's starting to slowly take in a different perspective, regardless.

The image/soundstage should be determined by the source material and sonic cues contained within, not from quirks of gear in the reproduction chain. Getting the room, speakers, and their interaction right, so that they get out of the way of the music, is the hard part. Audibly transparent electronics is the easy part.

Far too many, even audio enthusiasts who visit this board, know very little about room acoustics and speaker placement. Too many think that if you chuck enough money at the electronics, you have the major issues taken care of.

Though I must admit my bias is towards the scientific, as Bigus said, even as scientifically biased as I may be, we cannot prove a negative. We certainly, as scientists, know amplifiers measure differently. Even right down to the component level; e.g. a resistor has a tolerance to its specs. So, if we measure that exact resistor component across many different instances of the same model amplifier, it will likely measure differently. So, sure, we know there are differences between amplifiers. At a more gross level, we know that, for example, THD figures and slew rates and other measurable things are different between models. We know all sorts of things are different between two "x watts rated" amplifiers -- but we also, to date, know that in controlled experiments where both amplifiers are operated within their linear operating range that these differences are inaudible.

Exactly. I've measured dozens of amplifiers. With modern test equipment one can generally find repeatable and statistically significant differences between even the various channels of the same multichannel amplifiers. Two nominally identical monoblocks will measure differently from each other.

It is thus hard to escape the idea that at some point differences become so small that they are insignificant. Yet, how many audiophiles complain about audible differences of this kind? Of course any reasonable listening test will confirm that the audible differences between any two reasonable amplifier channels are moot.

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That said -- even removing biases, I wonder how many of these "I hear differences" things are true.

I think that they are true in the sense that they are not intentional falsehoods, and that they are usually also true on the grounds that they are the byproducts of naive listening evaluations. IOW the listener is perceiving a difference and in many cases there really is an audible difference due to the way the evaluation is done.
IOW they are true but irrelevant to the question of inherent audible differences among different pieces of audio gear of a given kind.

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Hard to drive loads, loud listening volumes at far away distances, and other factors can push some amplifiers pretty hard into their "non linear operating range."

Perhaps. More likely, inadequate level matchnig and badly done comparisons. Of course there are some ludicrous speaker loads out there - many branded with a M and a L, and sold by people (Company P) who should know better. But, there is no actual technical justification for building a speaker that is too hard for a good AVR to drive.

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Of course, this is a place we wouldn't want to stray into because I'd guess that what amplifiers do when they are "on the fringe" can very quite a bit due to circuit design.

You are speculating. I have spent years designing, bench testing and building power amplifiers.

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Oscillation would, I believe, increase THD and some designs would suffer more than others, no?

Oscillation often accompanies clipping. Avoid the clipping and you avoid the oscillation. Avoiding the clipping is a simple matter of having a powerful enough amplifier. If you run the numbers you will find that most home audio systems never ever see the sunny side of 50 wpc.

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So, how many of these uncontrolled "studies" have truly heard differences due to the fact that two amplifiers of similar wattage spec actually had different current capabilities (which, to the best of my knowledge really is the specification that matters most, no?).

Very few, only because the uncontrolled studies are already invalidated by stronger irrelevant influences, namely level matching and time synchronization. If you really want to do a sensitive listening test you need to be able to listen to the identical same music within a second or two. How many audiophiles have the resources (a switch box) to do this and actually do it? If you want to do a sensitive listening test you need some means for matching levels withn a couple of tenths of a dB. How many audiophiles have the resources to do this and actuallly do it?

I have now invalidated 99%+ of all listening tests that anybody has read of or actually done themselves, over the entire history of audio or just the last month. ;-)

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Of course, that difference was audible because one amplifier was running out of steam while the other kept on chugging. Further, its presense is probably no surprise and one which a controlled study would eliminate. But, still, one that could possibly be heard in the lisenting room of an uncontrolled experiment.

You appear to be making this far more complex than it usually is. In reality neither amplifier is usually even close to running out of steam. The whole test has already failed on the grounds of inadequate level matching and failure to actually listen to both amplifiers with the identical same music, and in quick succession.

If you want two amplifiers to sound different, simply play different musical selections or even the identical same musical selection at different times. That is what almost all audiophiles do. Therefore they pretty much universally perceive that all amplifiers sound different, and the way they compare them, they do!